CN111847702B - Method for treating cyanide-containing high-concentration ammonium sulfite wastewater - Google Patents

Method for treating cyanide-containing high-concentration ammonium sulfite wastewater Download PDF

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CN111847702B
CN111847702B CN201910354731.9A CN201910354731A CN111847702B CN 111847702 B CN111847702 B CN 111847702B CN 201910354731 A CN201910354731 A CN 201910354731A CN 111847702 B CN111847702 B CN 111847702B
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sulfite
cyanide
wastewater
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containing high
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CN111847702A (en
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杨本涛
李佳
崔泽星
魏进超
肖祈春
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Zhongye Changtian International Engineering Co Ltd
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    • C02F9/00—Multistage treatment of water, waste water or sewage
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/20—Treatment of water, waste water, or sewage by degassing, i.e. liberation of dissolved gases
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/24—Treatment of water, waste water, or sewage by flotation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/722—Oxidation by peroxides
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    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
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    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
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    • C02F2101/18—Cyanides

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Abstract

A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps: 1) removing sulfite ions: adding a sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate; 2) removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed; 3) and (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system. The invention provides a method for treating cyanide-containing high-concentration ammonium sulfite wastewater; firstly, removing sulfite ions and cyanide ions in high-concentration ammonium sulfite in sequence, and then adding alkali liquor to adjust the pH value of the solution. So that the addition amount of the alkali liquor for recovering the ammonia gas is reduced, and the cost for recovering the ammonia gas is reduced.

Description

Method for treating cyanide-containing high-concentration ammonium sulfite wastewater
Technical Field
The invention relates to a wastewater treatment method, in particular to a cyanide-containing high-concentration ammonium sulfite wastewater treatment method, and belongs to the field of sewage treatment.
Background
The ammonia desulphurization method can generate a large amount of ammonium sulfite wastewater, the ammonium sulfite wastewater belongs to ammonia nitrogen wastewater, the direct discharge of the ammonium sulfite wastewater can cause serious environmental pollution, toxic organisms in a water body can be greatly propagated in a short time, eutrophication phenomena such as red tide, water bloom and the like are generated, and meanwhile, dissolved oxygen in water is consumed, so that the life safety of fishes and shrimps and the health of people and livestock are seriously threatened.
At present, the method for treating/disposing ammonium sulfite mainly adopts evaporative crystallization to recover ammonium sulfite solid or evaporative crystallization to recover ammonium sulfate solid after oxidation, but dust enters into the solution, so that the recovered crystallization purity is low, and the problem of difficult crystallization is caused. If the ammonium sulfite solution is adjusted to be alkaline, ammonia nitrogen is converted into ammonia gas for recycling, the ammonia resource can be effectively recycled, and the operation cost is reduced. Chinese patent CN 108686477A reports a method for precipitating sulfite by using calcium oxide and then adjusting alkali to recover ammonia.
However, if cyanide is mixed in the flue gas, the cyanide enters the ammonium sulfite solution along with washing, and the cyanide-containing ammonium sulfite wastewater is formed. According to research, the method of the Chinese patent CN 108686477A is only applicable to waste water without cyanide. Cyanide and ammonia can form a buffer pair, and when the wastewater is adjusted to be alkaline and ammonia is recycled, the alkali consumption is increased rapidly, liquid alkali waste is caused, and the wastewater discharge amount is increased.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to remove sulfite ions and cyanide ions in high-concentration ammonium sulfite in sequence and then add alkali liquor to adjust the pH value of the solution. So that the addition amount of the alkali liquor for recovering the ammonia gas is reduced, and the cost for recovering the ammonia gas is reduced. The invention provides a method for treating cyanide-containing high-concentration ammonium sulfite wastewater, which comprises the following steps: 1) removing sulfite ions: adding sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate. 2) Removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed. 3) And (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system.
According to an embodiment of the present invention, there is provided a method for treating high-concentration ammonium sulfite wastewater containing cyanogen:
a method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) removing sulfite ions: adding sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate.
2) Removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed.
3) And (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system.
Preferably, the sulfite precipitator in step 1) is one or more of calcium oxide, magnesium oxide, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
Preferably, when the concentration of ammonium sulfite in the cyanide-containing high-concentration ammonium sulfite wastewater is higher than 0.1mol/L, preferably higher than 0.2mol/L, and more preferably higher than 0.3mol/L, the sulfite precipitator is one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
Preferably, the oxidant in step 2) is one or more of solid, liquid and gas.
Preferably, the oxidant is one or more of hydrogen peroxide, sodium hypochlorite, persulfate, potassium permanganate, potassium ferrate and ozone.
Preferably, in step 3), the lye is a solution containing a large amount of hydroxide ions and/or carbonate ions.
Preferably, the alkali liquor is specifically: one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide and potassium carbonate.
Preferably, the separation in the step 1) is implemented by filtration separation or suction filtration separation, and preferably, one or more methods of a gravity precipitation method, an air floatation method or a filtration method are used for implementing solid-liquid separation.
Preferably, the ammonia gas recovery system in the step 3) is one of a stripping tower, an ammonia still or a membrane separation system.
Preferably, the adjusting of the solution to a basic specific position in step 3): the pH of the solution is adjusted to 7-14, preferably 7.5-13, more preferably 8-12.
Preferably, the ratio of the molar amount of sulfite precipitant added in step 1) to the molar amount of sulfite ions in the wastewater is 1:0.1-3, preferably 1:0.5-2, more preferably 1: 0.8-1.5.
Preferably, the process conditions of step 1) are as follows: after the sulfite precipitant is added, the mixture is stirred for 0.1 to 24 hours, preferably 0.2 to 12 hours, and more preferably 0.5 to 6 hours. Standing for 0.5-48h, preferably 1-36h, preferably 2-24 h.
Preferably, the ratio of the molar amount of the oxidant added in step 2) to the molar amount of cyanide ions in the wastewater is 1:0.1-5, preferably 1:0.2-4, more preferably 1: 0.5-2.
Preferably, the process conditions of step 2) are as follows: after the oxidant is added into the filtrate, the mixture is stirred and reacted for 0.1 to 12 hours, preferably 0.2 to 6 hours, and more preferably 0.3 to 2 hours. The reaction temperature is 20 to 80 ℃, preferably 25 to 60 ℃, more preferably 30 to 50 ℃.
Preferably, the ratio of the molar amount of the alkali liquor added in the step 3) to the molar amount of the ammonium ions in the wastewater is 1:0.1-2, preferably 1:0.2-1.5, and more preferably 1: 0.5-1.2.
Preferably, the ammonia gas recovered by the ammonia gas recovery system in the step 3) is used for ammonia desulfurization.
The invention provides a method for treating cyanide-containing high-concentration ammonium sulfite wastewater, which has the following technical processes and technical principles: according to ion analysis, the wastewater mainly contains SO3 2-、CN-、NH4 +Ions, ammonia nitrogen and cyanide form a buffer pair, and the alkali consumption for converting ammonia nitrogen into ammonia gas is increased. The key to reducing the amount of alkali consumption is to destroy the buffering pair of ammonia nitrogen and cyanide, so CN is added-Oxidation is the core of the process. But due to SO3 2-The presence of ions, which have a strong reducing property, if not removed beforehand, leads to the oxidation of CN by the oxidizing agent-The ions are not complete and do not achieve the desired effect. Based on the analysis of the properties of each ion, pre-precipitated SO is proposed3 2-Ionic reoxidation of CN-And finally, adjusting alkali to realize ammonia recovery.
In the invention, sulfite ions and cyanide ions are removed in sequence, and then alkaline liquor is added to adjust the pH value of the wastewater, so that double decomposition reaction is carried out between hydroxide ions and ammonium ions in the alkaline liquor, and the ammonium monohydrate is generated. Ammonia monohydrate is unstable and decomposes into ammonia and water. Thereby, ammonia gas is extracted from the wastewater. The method mainly comprises the step of adding alkaline liquor containing hydroxyl ions or carbonate ions into the waste water. However, the method has poor effect on high-concentration ammonium sulfite containing cyanogen, because cyanide ions are easy to combine with ammonium ions in the wastewater to form a buffer solution. If cyanide ions exist, a large amount of alkali liquor is added to convert the ammonium ions in the wastewater into ammonia gas as much as possible for recycling, but the ammonium ions cannot be completely converted due to the cyanide ions, so that the cost of ammonia gas recycling is increased, and the recycling effect is poor. In addition, a large amount of alkali liquor is added to recover ammonia, so that a large amount of waste liquor is generated, troubles are brought to subsequent treatment, and secondary pollution is caused. Therefore, the cyanide ions in the wastewater need to be removed first. The cyanide ions are combined with reducibility, and can be reduced into carbon dioxide and nitrogen by adding an oxidant. However, since a large amount of sulfite ions are also present in the solution, the sulfite ions have extremely strong reducibility. When the oxidizing agent is added, the oxidizing agent will reduce sulfite ions to sulfate ions. Thus, if the oxidizing agent is added directly to the solution, a large amount of the oxidizing agent is also consumed. Thereby increasing the cost of ammonia recovery. Therefore, the method for extracting ammonia gas from the cyanide-containing high-concentration ammonium sulfite wastewater comprises the steps of firstly removing sulfite ions by using a sulfite ion precipitator, then adding an oxidant to reduce cyanide ions, and finally only adding alkali liquor to recover ammonium ions. The method aims at the problem that in the prior art, a large amount of alkali liquor is directly added, and the amount of the added alkali liquor is very small. And simultaneously, the conversion rate of ammonium ions into ammonia monohydrate is improved.
The above-mentioned reaction formula is as follows:
SO3 2-+ precipitant M → MSO3↓
CN-+ oxidant O → CO2+N2
NH4 ++OH-→NH3↑+H2O
In the present invention, after the sulfite precipitant dissolves in water, it will generate metal ions that can combine with sulfite ions to form a precipitate.
In the present invention, the precipitating agent selected comprises two classes, one being an oxide capable of reacting with water to form a hydroxide, the oxide comprising metal ions capable of combining with sulfite ions to form a precipitate such as: calcium oxide or magnesium oxide. Another class is water soluble and comprises salts of metal ions that can combine with sulfite ions to form precipitates, such as: ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, and ferrous nitrate.
The ion formula of the precipitate formed by the above substances is:
Ca2++SO3 2-＝CaSO3↓
Mg2++SO3 2-＝MgSO3↓
Fe2++SO3 2-＝FeSO3↓
Fe3++SO3 2-＝Fe2(SO3)3↓
the precipitating agents described in this embodiment include, but are not limited to, the sulfite precipitating agents listed.
In the present application, when the concentration of ammonium sulfite in the wastewater is lower than Amol/L, the sulfite precipitating agent is: calcium oxide and/or magnesium oxide. When the concentration of the ammonium sulfite in the wastewater is higher than Amol/L, the sulfite precipitator is: one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate. When the concentration is low, calcium oxide or magnesium oxide is adopted, so that the method is convenient and quick. The production cost is reduced. When the concentration is high, salts soluble in water, such as iron sulfate and ferrous sulfate, are required. Which can be sufficiently contacted with sulfite ions in the wastewater, thereby completely precipitating the sulfite ions. The production quality is improved. A is 0.1mol/L, preferably 0.2mol/L, more preferably 0.3 mol/L.
It should be noted that the selection condition of the precipitating agent can be judged according to different ammonium sulfite concentrations and by combining the actual operation condition of the enterprise.
In the present application, the oxidizing agent may be a solid, a liquid or a gas. When the oxidant is solid, the oxidant is preferably ground into powder and then put into the wastewater, and the reaction is fully performed by stirring, and when the solid oxidant is put into the wastewater, no bubbles are generated in the wastewater, which indicates that cyanide ions are completely removed. When the oxidant is liquid, the liquid oxidant is directly put into the wastewater, the reaction is fully performed through stirring, and after the liquid oxidant is put into the wastewater, bubbles are not generated in the wastewater any more, which indicates that the cyanide ions are completely removed. When the oxidant is gas, the gas oxidant is pumped from the bottom of the wastewater in the form of micro bubbles through a gas pump or an air pump. When the oxidant gas and cyanide ions undergo redox reaction to generate carbon dioxide and nitrogen, larger bubbles are generated in the wastewater. The reaction was allowed to proceed to completion by stirring, indicating complete removal of cyanide ions when no larger bubbles were formed in the wastewater.
In the present application, the preferred oxidant is one of hydrogen peroxide, sodium hypochlorite, persulfate, potassium permanganate, potassium ferrate or ozone, which are easily available and low in price.
In the present application, the lye contains a large amount of hydroxide ions or carbonate ions. The pH value of the waste water can be adjusted by adding alkali liquor into the waste water. When the pH value of the wastewater is adjusted to be alkaline, ammonium ions and hydroxide ions are combined to form ammonia monohydrate. The ammonia molecules then leave the wastewater due to instability of the ammonia monohydrate.
In the present application, the lye may be: one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide, potassium carbonate, etc. Solutions of these substances are all alkaline solutions.
In the present application, ammonia is recovered in one of a stripping column, an ammonia still, or a membrane separation system.
It should be noted that the ammonia gas combines with water to form ammonia monohydrate in a reversible reaction, and the chemical formula is as follows:
NH3+H2O＝NH3·H2O
the ammonia monohydrate is easily decomposed into ammonia gas and water under the action of heat, and the ammonia gas is separated out of liquid. The reaction formula is reacted in the direction of ammonia gas. Therefore, after the alkali liquor is added into the wastewater, the wastewater needs to be heated in the process of recovering the ammonia gas, so that the ammonia gas in the wastewater is separated out.
In the present application, in order to create an alkaline environment in the waste water, an alkaline solution is added to the waste water, and the pH of the waste water is adjusted to 7 to 14, preferably 7.5 to 13, more preferably 8 to 12. In an alkaline environment, sufficient hydroxide ions can be combined with ammonium ions.
In the present application, the precipitation may be removed by a gravity precipitation method, an air-float method or a filtration method. For example, the gravity sedimentation method is that a sedimentation tank is adopted to retain sediment in the sedimentation tank, and waste water is drained from the upper part of the sedimentation tank. Air flotation, i.e. spraying tiny air bubbles into the wastewater from the bottom, and the air bubbles are adhered around the precipitated substances. The sediment floats on the surface of the wastewater under the action of buoyancy, and can be removed by adopting a scraping mode. And (3) a filtration method, namely separating the precipitate in the wastewater into the wastewater by adopting a physical barrier mode.
In the present application, the ratio of the molar amount of sulfite precipitant added to the molar amount of sulfite ions in the wastewater is, as the case may be, from 1:0.1 to 3, preferably from 1:0.5 to 2, more preferably from 1:0.8 to 1.5. Ensuring that sufficient sulfite precipitant reacts with sulfite ions.
In the present application, after the sulfite precipitant is added, stirring is carried out for 0.1 to 24 hours, preferably for 0.2 to 12 hours, more preferably for 0.5 to 6 hours. Standing for 0.5-48h, preferably 1-36h, preferably 2-24 h. The sulfite precipitant is fully reacted with sulfite ions by stirring for a long time. The long-time standing is beneficial to precipitate precipitates and realizes separation.
In the present application, the ratio of the molar amount of the oxidizing agent added to the molar amount of the cyanide ions in the wastewater is, as the case may be, 1:0.1 to 5, preferably 1:0.2 to 4, more preferably 1:0.5 to 2. Ensuring that sufficient oxidant reacts with the cyanide ions. Generally, the method is to detect the content of cyanide ions in wastewater. And determining the addition amount of the oxidant by combining the properties of the selected oxidant so that the addition amount of the oxidant meets the requirements of the cyanide ions.
In the present application, the process conditions for oxidizing cyanide ions are: after the oxidant is added into the filtrate, the mixture is stirred and reacted for 0.1 to 12 hours, preferably 0.2 to 6 hours, and more preferably 0.3 to 2 hours. Ensuring that the cyanide ion is fully reacted. The reaction temperature is 20 to 80 ℃, preferably 25 to 60 ℃, more preferably 30 to 50 ℃. Ensuring the speed of oxidizing cyanide ions. The reaction time is shortened.
In the present application, the ratio of the molar amount of the alkaline solution added to the molar amount of the ammonium ions in the wastewater is, as the case may be, from 1:0.1 to 2, preferably from 1:0.2 to 1.5, more preferably from 1:0.5 to 1.2. As the sulfite ion is precipitated, oxides such as calcium oxide and magnesium oxide may be added. The oxides dissolve in water to form hydroxides, which also adjust the pH of the solution. Therefore, in the step of adding alkali liquor to recover ammonia gas in the last step, alkali liquor is added according to actual conditions. The production cost of enterprises can be reduced.
In this application, for the environmental protection, the waste water after the deamination is deposited in the environmental protection jar and is waited further processing.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the scheme, the use amount of the alkali liquor in the ammonia gas recovery process can be effectively reduced, so that the ammonia gas recovery cost is reduced;
2. according to the scheme, the characteristics of cyanide-containing high-concentration ammonium sulfite wastewater are combined, and sulfite radicals and cyanide ions in the solution are sequentially removed, so that ammonia is more fully recovered;
3. the scheme of the invention greatly reduces the input amount of alkali liquor, simultaneously greatly reduces the amount of discharged water and protects the environment;
4. the process route of the scheme of the invention is safe and reasonable, and the risk of production accidents does not exist;
5. the raw materials used in the scheme of the invention are easily purchased in the market, the product cost is low, and secondary pollution can not be caused.
Drawings
FIG. 1 is a process flow diagram of the method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to the present invention;
FIG. 2 is a schematic representation of the lye pH values of example 2 and comparative examples 1 to 4 in a comparative experiment.
Detailed Description
According to an embodiment of the present invention, there is provided a method for treating high-concentration ammonium sulfite wastewater containing cyanogen:
a method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) removing sulfite ions: adding a sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate;
2) removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed;
3) and (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system.
Preferably, the sulfite precipitator in step 1) is one or more of calcium oxide, magnesium oxide, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
Preferably, when the concentration of ammonium sulfite in the cyanide-containing high-concentration ammonium sulfite wastewater is higher than 0.1mol/L, preferably higher than 0.2mol/L, and more preferably higher than 0.3mol/L, the sulfite precipitator is one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
Preferably, the oxidant in step 2) is one or more of solid, liquid and gas.
Preferably, the oxidant is one or more of hydrogen peroxide, sodium hypochlorite, persulfate, potassium permanganate, potassium ferrate and ozone.
Preferably, in step 3), the lye is a solution containing a large amount of hydroxide ions and/or carbonate ions.
Preferably, the alkali liquor is specifically: one or more of sodium hydroxide, sodium carbonate, potassium hydroxide, sodium carbonate, sodium hydroxide and potassium carbonate.
Preferably, the separation in the step 1) is implemented by filtration separation or suction filtration separation, and preferably, one or more methods of a gravity precipitation method, an air floatation method or a filtration method are used for implementing solid-liquid separation.
Preferably, the ammonia gas recovery system in the step 3) is one of a stripping tower, an ammonia still or a membrane separation system.
Preferably, the adjusting of the solution to a basic specific position in step 3): the pH of the solution is adjusted to 7-14, preferably 7.5-13, more preferably 8-12.
Preferably, the ratio of the molar amount of sulfite precipitant added in step 1) to the molar amount of sulfite ions in the wastewater is 1:0.1-3, preferably 1:0.5-2, more preferably 1: 0.8-1.5.
Preferably, the process conditions of step 1) are as follows: after the sulfite precipitator is added, stirring for 0.1-24h, preferably 0.2-12h, more preferably 0.5-6 h; standing for 0.5-48h, preferably 1-36h, preferably 2-24 h.
Preferably, the ratio of the molar amount of the oxidant added in step 2) to the molar amount of cyanide ions in the wastewater is 1:0.1-5, preferably 1:0.2-4, more preferably 1: 0.5-2.
Preferably, the process conditions of step 2) are as follows: adding an oxidant into the filtrate, and then stirring and reacting for 0.1-12h, preferably 0.2-6h, more preferably 0.3-2 h; the reaction temperature is 20 to 80 ℃, preferably 25 to 60 ℃, more preferably 30 to 50 ℃.
Preferably, the ratio of the molar amount of the alkali liquor added in the step 3) to the molar amount of the ammonium ions in the wastewater is 1:0.1-2, preferably 1:0.2-1.5, and more preferably 1: 0.5-1.2.
Preferably, the ammonia gas recovered by the ammonia gas recovery system in the step 3) is used for ammonia desulfurization.
Example 1
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) removing sulfite ions: adding a sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate;
2) removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed;
3) and (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system.
Example 2
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) removing sulfite ions: adding calcium oxide into the wastewater to generate calcium sulfite precipitate, stirring for 12h, and filtering and separating after the reaction is finished to obtain filtrate;
2) removing cyanide ions: adding hydrogen peroxide into the filtrate, and reacting cyanide ions with the hydrogen peroxide for 0.5h at 40 ℃; obtaining solution for removing cyanide ions;
3) and (3) ammonia gas recovery: adding sodium hydroxide into the solution from which cyanide ions are removed, and adjusting the solution to be alkaline, wherein the pH value is 9-12; recovering ammonia gas through an ammonia gas recovery system;
wherein: the concentration of the sulfurous acid in the cyanide-containing high-concentration ammonium sulfite wastewater is 0.08 mol/L; the ratio of the molar weight of calcium oxide added in the step 1) to the molar weight of sulfite ions in the wastewater is 1: 0.6; step 2), the ratio of the molar weight of the added hydrogen peroxide to the molar weight of cyanide ions in the wastewater is 1: 1; and 3) the ratio of the molar weight of the added sodium hydroxide to the molar weight of the ammonium ions in the wastewater is 1: 0.8.
Example 3
Example 2 is repeated, except that the concentration of the sulfurous acid in the cyanide-containing high-concentration ammonium sulfite wastewater is 0.15mol/L, the calcium oxide is replaced by ferrous sulfate in the step 1), and suction filtration separation is adopted; the ratio of the molar weight of the ferrous sulfate added in the step 1) to the molar weight of the sulfite ions in the wastewater is 1: 1.
Example 4
Example 2 is repeated, except that the concentration of the sulfurous acid in the cyanide-containing high-concentration ammonium sulfite wastewater is 0.28mol/L, and the potassium ferrate is used to replace the hydrogen peroxide in the step 2); the ratio of the molar weight of the potassium ferrate added in the step 2) to the molar weight of cyanide ions in the wastewater is 1: 0.4. The reaction time is 2h, and the reaction temperature is 25 ℃;
example 5
Example 2 was repeated except that the concentration of sulfurous acid in the cyanide-containing high-concentration ammonium sulfite wastewater was 0.3mol/L, and potassium carbonate was used in place of sodium hydroxide in step 3); adjusting the pH value to 8-9; and 3) the ratio of the molar weight of the potassium carbonate added in the step 3) to the molar weight of the ammonium ions in the wastewater is 1: 0.4.
Example 6
Example 2 was repeated except that the stirring time was 6 h;
comparative example 1
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) directly adding alkali liquor into the wastewater for ammonia recovery.
Comparative example 2
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) firstly, independently adding a precipitator into the wastewater to remove sulfite ions;
2) then adding alkali liquor into the waste water for ammonia recovery.
Comparative example 3
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) firstly, independently adding an oxidant into the wastewater to remove cyanide ions;
2) then adding alkali liquor into the waste water for ammonia recovery.
Comparative example 4
A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) firstly, independently adding an oxidant into the wastewater to remove cyanide ions;
2) adding a precipitator into the wastewater separately to remove sulfite ions;
3) and finally, adding alkali liquor into the wastewater to recover ammonia.
Experiments were conducted in the manner of example 1 and comparative examples 1 to 4 described above. The experimental method comprises the following steps: the same amount of the same cyanide-containing high-concentration ammonium sulfite wastewater was subjected to the experiments in the same manner as in example 1 and comparative examples 1 to 4, respectively. In the experimental process, calcium hydroxide is used as a precipitator, and potassium permanganate is used as an oxidant. The volume of the treated wastewater can be effectively controlled by adopting the solid precipitator and the oxidant. After the precipitant or the oxidant is added, the volume of the wastewater can be regarded as unchanged. The alkali liquor added is as follows: sodium hydroxide solution at PH 13. The results of the experiment are shown in FIG. 2.
As can be seen from FIG. 2, the wastewater is treated by the method of example 2, and in the ammonia recovery link, the ratio of the alkaline solution is as follows: 0.28. substantially less than 1.19 for comparative example 1, 0.61 for comparative example 2, 0.78 for comparative example 3 and 0.79 for comparative example 4. Therefore, the method of example 1 is adopted to treat the wastewater, and the input amount of alkali liquor during deamination can be greatly reduced. Meanwhile, the technical scheme provided by the invention can effectively remove sulfite ions and cyanide ions in the wastewater without generating secondary pollution. Note: the lye ratio means the ratio of the volume of lye to the volume of wastewater.

Claims (24)

1. A method for treating cyanide-containing high-concentration ammonium sulfite wastewater comprises the following steps:
1) removing sulfite ions: adding a sulfite precipitator into the wastewater to generate sulfite precipitate, and separating after the reaction is finished to obtain filtrate;
2) removing cyanide ions: adding an oxidant into the filtrate, and reacting cyanide ions with the oxidant to obtain a solution from which the cyanide ions are removed;
3) and (3) ammonia gas recovery: and adding alkali liquor into the solution from which the cyanide ions are removed, adjusting the solution to be alkaline, and recovering ammonia gas through an ammonia gas recovery system.
2. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 1, which comprises: the sulfite precipitator in the step 1) is one or more of calcium oxide, magnesium oxide, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
3. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 2, characterized in that: when the concentration of ammonium sulfite in the cyanide-containing high-concentration ammonium sulfite wastewater is higher than 0.1mol/L, the sulfite precipitator is one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
4. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 2, characterized in that: when the concentration of ammonium sulfite in the cyanide-containing high-concentration ammonium sulfite wastewater is higher than 0.2mol/L, the sulfite precipitator is one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
5. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 2, characterized in that: when the concentration of ammonium sulfite in the cyanide-containing high-concentration ammonium sulfite wastewater is higher than 0.3mol/L, the sulfite precipitator is one or more of ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate and ferrous nitrate.
6. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 1, which comprises: the oxidant in the step 2) is one or more of solid, liquid and gas.
7. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 6, which comprises: the oxidant is one or more of hydrogen peroxide, sodium hypochlorite, persulfate, potassium permanganate, potassium ferrate and ozone.
8. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 1, which comprises: in the step 3), the alkali liquor is a solution containing a large amount of hydroxide ions and/or carbonate ions.
9. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 8, characterized in that: the alkali liquor comprises the following specific components: one or more of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate.
10. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, wherein the separation in step 1) is performed by filtration or suction filtration.
11. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 10, wherein the separation is carried out by one or more of gravity precipitation, air flotation or filtration.
12. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: the ammonia gas recovery system in the step 3) is specifically one of a stripping tower, an ammonia still or a membrane separation system.
13. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: the adjusting the solution to be alkaline in the step 3) is specifically as follows: adjusting the pH of the solution to 7-14.
14. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: the adjusting the solution to be alkaline in the step 3) is specifically as follows: adjusting the pH of the solution to 7.5-13.
15. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: the adjusting the solution to be alkaline in the step 3) is specifically as follows: adjusting the pH of the solution to 8-12.
16. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: the ratio of the molar weight of the sulfite precipitator added in the step 1) to the molar weight of sulfite ions in the wastewater is 1: 0.1-3; and/or
The process conditions of the step 1) are as follows: adding sulfite precipitator, and stirring for 0.1-24 h; standing for 0.5-48 h.
17. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 16, characterized in that: the ratio of the molar weight of the sulfite precipitator added in the step 1) to the molar weight of sulfite ions in the wastewater is 1: 0.5-2; and/or
The process conditions of the step 1) are as follows: adding sulfite precipitator, and stirring for 0.2-12 h; standing for 1-36 h.
18. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 16, characterized in that: the ratio of the molar weight of the sulfite precipitator added in the step 1) to the molar weight of sulfite ions in the wastewater is 1: 0.8-1.5; and/or
The process conditions of the step 1) are as follows: adding sulfite precipitator, and stirring for 0.5-6 h; standing for 2-24 h.
19. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: step 2), the ratio of the molar weight of the oxidant to the molar weight of cyanide ions in the wastewater is 1: 0.1-5; and/or
The process conditions of the step 2) are as follows: adding an oxidant into the filtrate, and stirring for reaction for 0.1-12 h; the reaction temperature is 20-80 ℃.
20. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 19, characterized in that: step 2), the ratio of the molar weight of the oxidant to the molar weight of cyanide ions in the wastewater is 1: 0.2-4; and/or
The process conditions of the step 2) are as follows: adding an oxidant into the filtrate, and stirring for reaction for 0.2-6 h; the reaction temperature is 25-60 ℃.
21. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 19, characterized in that: step 2), the ratio of the molar weight of the oxidant to the molar weight of cyanide ions in the wastewater is 1: 0.5-2; and/or
The process conditions of the step 2) are as follows: adding an oxidant into the filtrate, and stirring for reaction for 0.3-2 h; the reaction temperature is 30-50 ℃.
22. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to any one of claims 1 to 9, characterized by: step 3), the ratio of the molar weight of the added alkali liquor to the molar weight of ammonium ions in the wastewater is 1: 0.1-2; and/or
And (3) the ammonia gas recovered by the ammonia gas recovery system in the step 3) is used for ammonia desulphurization.
23. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 22, characterized in that: the ratio of the molar weight of the alkali liquor added in the step 3) to the molar weight of the ammonium ions in the wastewater is 1: 0.2-1.5.
24. The method for treating cyanide-containing high-concentration ammonium sulfite wastewater according to claim 22, characterized in that: the ratio of the molar weight of the alkali liquor added in the step 3) to the molar weight of the ammonium ions in the wastewater is 1: 0.5-1.2.
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